[Three cases of de novo aneurysms].

We report 3 cases of de novo aneurysms that developed long after neck clipping of the initial aneurysms (range, 7 to 20 years, mean 12 years). Case 1 was a 58-year-old female who had undergone clipping of a ruptured aneurysm 17 years previously. Ten years later, she suffered another subarachnoid hemorrhage due to rupture of a new aneurysm, for which neck clipping was performed. Another seven years later, she had a third subarachnoid hemorrhage, and angiography revealed a new aneurysm, for which neck clipping was performed. Case 2 and 3 were both 68-year-old females who had suffered subarachnoid hemorrhage with two aneurysms and had undergone neck clipping for them respectively, 20 years and 12 years previously. Each patient was admitted to our hospital with complaints of headache, diplopia, vertigo, etc., and newly formed aneurysms were detected by magnetic resonance angiography. Conventional angiography revealed three and one new aneurysms, respectively. Since case 1 was a special case of multiple aneurysms in which lesions appeared in series rather than in parallel, all three patients harbored multiple aneurysms. It is recommended that patients with multiple aneurysms, especially those after a long period postoperatively, undergo periodic examination on an outpatient basis to detect formation of de novo aneurysms by magnetic resonance angiography or 3D-CT angiography.